Clutch facing and process of making same



Patented Mar. 30', 1926.

UNITE-D3 STATES v 7 ,928 E .QFEICE.-.

summit. smrson, or BRIDGEPORT, CONNECTICUT, AssreNoR naynnsros COMPANY, OF BRIDGEPOBT, CONNECTICUT, A CORPORATION orv CoimnCTiCuT.

CLUTCH FACING PROCESS OF MAKING SAME.

11' 0 Drawing.

To all whom it may cmwern:

Be it known that I, SUMNER SIMPSON, a citizen of the United States, residing at Bridgeport, county of Fairfield, State of Connecticut, have invented an Improvement in Clutch Facings and Processes of Making Same, of which the following is a specification.

This application isa continuation in part of application Serial Number 221,002, filed March 7, 1918.

The invention relates generally to proc esses of producing clutch facings, with more particular reference to the various types of automobile clutches. It is well known that there are two highly important qualities which, on account of the nature of the work they are called upon to perform,

should be. possessed by clutch facings in general, first, they should have a uniformly high coefiicient of friction, and second, they should be exceedingly tough in order to withstand the excessive wearing strains of use. Particularly in the case of automobile clutches, the replacing of the clutch rings is a laborious and expensive operation, and every efifort has been made to produce these rings from material having a requisitely high and uniform coeflicient of friction and adapted to withstand the strains of use for the longest possible period of time.

It will be apparent, moreover, thatin addition' to the two essential qualities mentioned above, in View of the heat which is produced by the friction, clutch rings or facings should be constructed of material capable of being brought to high temperatures without undergoing either physical or chemical change, and on this account asbestos has been generally employed as the base for clutch-ring material, for asbestos is not only Well known to be capable of withstanding high temperatures without chemical or physical change, but it also possesses the requisitely high coefiicient of friction, and good wearing qualities.

In the mining of asbestos, the mine run includes relatively long fibers, known as crude asbestos, the only part of the'run that can be used for spinning, and relatively short fibers, known as fiber-asbestos, which cannot be spun. The crude asbestos is shipped tov the spinning mill, where it is crushed, Opened, carded, roved and spun,

" Application filed June 4, 1921. Serial NO. 475,146.

and then twisted around a metallic core,

usually small-gauge brass or copper wire,

chemically treated and baked at the proper.

temperature to make them coherent, tough, relatively hard, and possessed of the desired coeflicient of friction.

lVith respect to this old process, it will be of the mined asbestos can be employedthat is to say, the crude or long-fiber asbestosand, second, that the spinning of these long fibers into filaments, the twisting of these filaments around the metallic core to form reinforced metallic yarn, the weaving of this yarn into fabric, the forming of the fabric into rings of the proper dimensions, and the treating and baking of these noted, first, that only a certain selective part second, because woven. fabric, however treated, is always subject to a tendency to ravel, particularly after having been subjected to wear for an uncertain length of time.

The present invention has in view a process of producing asbestos-base clutch rings, in which carding, roving, spinning, twisting and weaving of the raw material is entirely dispensed with; furthermore, a process in which the short-fiber asbestos'of the mine run may be utilized, and furthermore, a process by which may be produced integral asbestos-base rings of a homogeneous character, not only of uniform dimensions and contour, but of a character to retain the original size, contour, homogeneity andother qualities throughout long-continued use thereof.

The present invention relates to the formation of a friction facing, as for examplei a clutch ring in which the facing is saturate with the asphaltic binder in certain propor- View. This asphaltic binder may be an artificial asphalt or a natural asphalt cut back with a suitable flux oil or a mixture of an artificial and natural asphalt. Such natural asphalts as gilsonite, elaterite and wurt-v zelite, suitably out back or mixed with other softer asphaltic compounds may be used. Where an artificial asphalt is used, it may be either an asphalt prepared from the purely asphaltic base oils such as Mexican or California oils or from the semi-asphaltic base oils such as those of the Oklahoma or Kansas mid-continent fields. In certain cases, the parafl'ine base oils might perhaps be used. The asphaltic compound-of this character may either be a straight petroleum residum produced, preferably by the steam distillation of crude petroleum or it may be an air blown asphalt or asphaltic product compound produced from steam distillation partly .and partly from air blowing.

One of the characteristic features of the present invention relates to the percentage of binder incorporated in the finished ring. I have discovered that the percentage of binder very materially affects the tensible strength and Brinnell hardness of .the ring and has an important bearing on the com-- mercial value thereof. For example the use of from about ten per cent to about twenty per cent is highly desirable. It is to be understood, however, that some variation from the above ercentages may be allowed in such cases either insomewhat below ten per cent or somewhat above twenty per cent. These percentages refer to the weight of binder in the finished product as against the weight of dry ring before saturation.

Among other analogous ways of carrying out 111 improved process, I may take the shortber asbestos stock from the mines, mix the same by any approved process of saturation with the properproportion of a suitable liquid binder or binding compound, mold the same under compression to the desired form and size and then remove the facings from the molds and thoroughly dry the same either in the air or by passing them through a suitable oven. In this manner, not only "am I enabled to utilize what is known as low-grade asbestos fiber, but to produce clutch rings which experiments have demonstrated will wear longer, give much better results and be more eflicient in every way than the woven endless or joined rings or facings. Furthermore by molding under compression, a ring or facing from a homo geneous mass of plastic material, the process is carried on without the excessive waste of material which cannot be avoided under present methods of forming these rings from woven tape. Furthermore, it will be apparent -.that in mixing the materials to produce the plastic mass from which the rings are molded, I am enabled to insure saturation of the asbestos fiber with the binding material to a much more nearly perfect degree than is possible in the attempted saturation of rings formed from woven tape.

Instead of molding the facings, I can, and sometimes prefer to, form the mixture into a sheet which is subsequently cut into pieces of the required shape and size. Such sheets can be made without the loss of any advantages above mentioned as obtained by molding each facing separately.

I have referred to molding the facings as one method of carrying out the invention, and also forming the mixture into a sheet and subsequently cutting into pieces of the oven. This baking should be continued until the required strength and hardness has been obtained.

I may still further improve the product of my novel process by incorporating in the plastic compound, prior to compression, metal wire, preferably copper or brass wire which may be in the form of rings, or a woven mesh, or short lengths of wire may be indiscriminately dispersed throughout the mass. This metallic reinforcement imparts to the finished rings additional strength, rigidity and toughness.

It is required that the fibers and the binder be thoroughly commingled or amalgamated through any preferred manner of agitation in a suitable container for such period of time as may be required to insure complete saturation of the asbestos fibers, and that after molding or sheeting the rings or sheets be thoroughly dried and baked, ordinarily in a heated oven.

The proportions'of the ingredients to be employedis a matter of individual judgment. The ultimate object is to produce a solid homogeneous body in which the fiber predominates. Therefore, just enough of the binding liquid should be employed .to saturate the fiber to an extent which insures substantial sodility and homogeneityunder compression. I have found that from 10% to 20% of the binder referred to gives the desired results and I am now referring to weight of binder as against the weight of dry ring before saturation. It is to be understood, hqwever, that some modification 'of these proportions is permissible, depending on the tensile strength and hardness required and also somewhat on the character of the asbestos fibre used.

In case the loose fibre is to besaturated I tweets twenty parts by weight of asphaltic binder. Various material may be used for a bind- 50 A flux, such as benzol, gasoline, or petroleum distillates of higher boiling points, is added and the mixture churned till the binder has covered all the asbestos fibres.

In case the asbestos fibre is formed into sheets and cut into pieces of the required shape and size before saturation, the saturation is effected by immersion in a mixture of the asphaltic material and the flux and the immersion allowed to continue until the pieces have taken up sufficient saturant to leave about ten to about twenty per cent after subsequent baking.

The quantity of the saturant which is taken up by the asbestos fibre is determined by the gravity of the saturant,.its viscosity and the duration of the immersion. For example, I have found that with a mixture of about two parts asphaltic material with one of flux at a temperature from about seventy degrees F. to about three hundred degrees F. depending upon the flux used,

from about ten per cent to about twenty per cent of residual saturant is taken up in one hour. Residual saturant is the quantity 7 of asphaltic material which remains in the ring after curing.

Uniform density is a matter of prime consideration in the production of these rings,

for if. the density varies the effects of wearing will be unevenly distributed and thus tend to shorten the useful life of the product. By saturating and thoroughly intermingling the fibers rior to compression practically uniform ensity of the finished product is insured.

It should be noted that inall asbestos yarn as now manufactured, the use of a certain amount of cotton is necessary in order that the asbestos fibers may be picked up and carried over the card. The existence of even a comparatively small amount of cotton in clutch-ring material is manifestly objectionable, but its presence therein has been necessitated in the manufacture of rings from woven asbestos. It is highly important that the product of the present process is wholly free from cotton or any equivalent thereof.

er, but in certain circumstances I have found asphaltic compounds, which may be greatly varied, are particularly suitable, since they readily penetrate the fibres and, upon drying, not onlyeifect the desired cohesion of the asbestos particles, but waterproof and oilproof the product.

By using the loose fiber, this process not only eliminates many expensive operations in making a fabric, but permits the use of low grade asbestos withshort fibres.

Having thus described my invention, I claim:

1. The process of making clutch facings which consists in providing an element composed of unwoven asbestos fibers impregnated with a saturant containing an asphaltic binder, and then curing the element until the required strength and hardness has 'been secured, the amount of saturant being from about 10% to about 20% of the weight of fiber.

2. The process of making clutch facings. which consists in providing an element composed of unwoven asbestos fibers impregnated with a saturant containing an asphalt cut back with a suitable flux, and then curing the element until the required strength and hardness has been secured, the amount of saturant being from about 10% to about 20% of the weight of fiber.

3. A clutch facing comprisin an element formed of unwoven asbestos fi ers impregnated with a saturant containing an asphaltic binder and cured to give the required stren h and hardness, the amount of saturant in from' about 10% of the weight of fiber.

4. A clutch facing comprising an element formed of unwoven asbestos fibers impregnated with a saturant containing an asphalt cut back with a suitable flux and' cured to give the required strength and hardness the amount of the saturant bein from about 10% to about 20% of the weig t of fiber.

In testimony whereof I aflix my signature.

' SUMNER SIMPSON.

to about 20% 

